Pevono Power Supply, common failure, how to repair. Upgrade discussion

[JBurdman7]

I'm referring to the Pevono PS305 line of budget bench power supplies https://www.amazon.com/Pevono-Digital-Adjustable-Switching-Regulated/dp/B076TMJB35/ref=sr_1_1??tag=parts099-20, also sold as "Sky TopPower" STP30* models https://www.amazon.com/Adjustable-Switching-Regulated-Alligator-Spectrophotometer/dp/B07GCJ5QHF/ref=sr_1_1?tag=parts099-20 and the 4 digit / 60V / 10A variants. Before people complain about my cheap PSUs, I also have an Agilent E3631A for when I care to send the very best, which, TBH, is not all that often. I use two Pevonos pretty hard.

The Pevono units have a major problem with the STP75NF75 https://www.st.com/resource/en/datasheet/stb75nf75.pdf output transistor shorting. I have fried the output MOSFET on one or the other unit every year so far. It's easy to do. I suspect that just going in to current limit while set to the highest voltage can kill them but I have not tempted fate to test my theory. At least the safety kicks in and kills the output. 12VoltVids on YouTube covers the repair here The transistor is right on top so repair could not be easier.

The diagram for the STP75NF75 shows a body zener. I don't know the Voltage of it. I was wondering if anyone here had a suggestion as to what could potentaially be added to help increase the life of these MOSFETs. Perhaps a power diode to shunt any reverse connections. Maybe a 45ishV zener external and in parallel with the body zener in case an inductive spike is coming from the unit itself? I have a 45V zener but it is tiny and perhaps adding that would just be asking for trouble. There are 40VBO BJTs as per Kangaroo Dave's shunt suggestion but they run $12 each. I don't see that making sense. While downtime is annoying, the STP75NF75 can run a buck each from some suppliers.

Any thoughts? Please share.

[akimpowerscr]

Welcome to the forum.

Don't you think it would be necessary for you to provide the diagrams of this power supply so that your questions can be answered?

[JBurdman7]

Don't you think it would be necessary for you to provide the diagrams of this power supply so that your questions can be answered?

I'd be glad to if I had them. It's just a cheap switching supply. This is literally the only PDF I know of online about the unit, and it is useless
https://componentfun.com/media/resources/PevonoPS305manual.pdf

There are a few caps across the output. I don't see any reverse polarity protection or anything else. It seems to rely on the STP75NF75 body zener for protection and that is not cutting it.